Topic: 2.5 Block Differences

[RNandKT]

OK I did some searching and I was unable to find a clear answer to this.

I picked up another 97 TJ (will be my sons Jeep) with a blow 2.5 (hole in the side of the block). I was given a donor motor from a YJ (I think it was a 94) and we are going to use that to rebuild.

So I know the head is ever so slightly different and we can use the head from the TJ so not worried about that, but when I look up rebuild kits it wants me to specify year. Are there any short block differences between the YJ and TJ 2.5's? We will reuse all the externals from the TJ motor, so my only concern is the short block. Anyone know on this.

[RNandKT]

Oh and another side Question, has anyone ever put the famous Mopar Purple CAM in a Fuel Injected TJ/YJ? I have a lead on a purple CAM kit (Camshaft lifters springs etc) but not sure it is compatible with the fuel injection system.

[Jeffy]

I don't believe there are any major differences between the blocks...

There are many who have installed the Mopar cams.  I was even going to till I moved to a emission controlled state.  The cams were designed to be used in late TBI's and early MPFI engines.  Jeep Motorsports was involved in SCORE and SCCA events back in the 80's and early 90's.

[RNandKT]

Thanks

The guy selling the Mopar Purple CAM is selling it for $250 for the kit (CAM lifters spings etc) which since my 14 year old son has to come up with half the money of anything we put into it seems steep to him. So not sure if it is worth the money. If it isn't a really noticable difference than $250 goes a long way towards lift or other items.

[Jeffy]

Thanks

The guy selling the Mopar Purple CAM is selling it for $250 for the kit (CAM lifters spings etc) which since my 14 year old son has to come up with half the money of anything we put into it seems steep to him. So not sure if it is worth the money. If it isn't a really noticable difference than $250 goes a long way towards lift or other items.

Well, there are 5 different cam profiles, IIRC.  So it really depends on which cam it is.  You can see the different part numbers and profile info in the FAQ.

[RNandKT]

The part numbers he lists don't seem to match any of the part numbers in the FAQ list, the specs he lists are the same as P4529656 except for the valve lift.

This is what he has listed

For sale. Mopar performance cam kit. Comes with mopar purple cam p# p4529314. Followers or lifters part# p4349147. Valve springs p# p4286813. Valve seals p# p4349121. Matched set.
Fits Chrysler dodge Plymouth mopar turbo 2.2 or 2.5

Specs. Lift 46 duration 240 overlap 24 centerline 108.

For me I would only change the CAM is I was getting some more Torque, HP is not really a concern, for these motors I would much rather improve the low end torque. The low Duration on this CAM and the higher lift, I would assume this CAM would favor torque, but my knowledge of CAM specs is somewhat limited. I am unable to find his part numbers listed anywhere else so I am not even 100% sure it is the correct cam for a Jeep 2.5

[Jeffy]

The part numbers he lists don't seem to match any of the part numbers in the FAQ list, the specs he lists are the same as P4529656 except for the valve lift.

This is what he has listed

For sale. Mopar performance cam kit. Comes with mopar purple cam p# p4529314. Followers or lifters part# p4349147. Valve springs p# p4286813. Valve seals p# p4349121. Matched set.
Fits Chrysler dodge Plymouth mopar turbo 2.2 or 2.5

Specs. Lift 46 duration 240 overlap 24 centerline 108.

For me I would only change the CAM is I was getting some more Torque, HP is not really a concern, for these motors I would much rather improve the low end torque. The low Duration on this CAM and the higher lift, I would assume this CAM would favor torque, but my knowledge of CAM specs is somewhat limited. I am unable to find his part numbers listed anywhere else so I am not even 100% sure it is the correct cam for a Jeep 2.5

That's not a Jeep cam.  That's for a Dodge/Plymouth Omni/Horizon Turbo 2.2 and 2.5L.  Completely different engines.

[sharpxmen]

heads are the same, only difference the YJ head has a temp sensor towards the firewall on the driver's side, just leave the sensor in as a plug

[Wrench]

There are some differences in the 2.5 blocks, but those may just be differences between the XJ 2.5 and Wrangler engines.  My 1984 XJ 2.5 was a bit different than the '93 YJ 2.5.  Intake and exhaust patterns, engine mounts, and bellhousing are identical, though.

-'84-'85 use smaller diameter head bolts
-somewhere around 1990 the valve spring retainers shrunk in size, tapered (beehive) springs replaced the old straight ones, and the keepers went 3-groove instead of 1.
-the XJ timing cover has some small differences in bolt pattern where the alternator brackets mount.
-the XJ 2.5 crank is longer at the harmonic balancer, and belt alignment is about 1/4" further from the block than the YJ.
-the early years had a fuel pump mount/hole in the the block, the later years have this blocked out and it is just a coil mount.
-though the oil pans are identical, the later model oil pan gaskets are reusable rubber, and seal way better.

[sharpxmen]

There are some differences in the 2.5 blocks, but those may just be differences between the XJ 2.5 and Wrangler engines.  My 1984 XJ 2.5 was a bit different than the '93 YJ 2.5.  Intake and exhaust patterns, engine mounts, and bellhousing are identical, though.

this engine was revised in '86 prior to YJs being fitted with it, that is when I think most of the changes you mentioned occurred. heads are different prior to 91 if I recall correctly. For MPFI YJ era engines (91-95) there are no major differences compared to TJ I4 engines and major parts (not accessories) are in general interchangeable (some differences: oil pan drain plug position, extra temp sensor whole in the head, slightly different cam timing)

[RNandKT]

OK So resurrecting an old thread to get some input on CAM's again. Was trying to search but got a lot of info, but nothing exactly what I was looking for.

So I have finally gotten around to rebuild my 4 cyl. I cam across a place that I am buying my rebuild kit from and they will do CAM regrinding as well for only an extra $90. I figured choosing one of the purple cam specs would be the wiseest, but not sure which to choose. The 4 cyl will have the upgraded 4 hole injectors and the larger throttle body, and down the road when I need to replace the exhaust I will open it up a bit, but other than that stock. So I would like to pick CAM specs that will bump performace a little without needing to mess with the ECU at all. I would prefer to avoid replacing valve springs as well, but if there isn't a way around that it would't be a big deal.

So CAM experts which performance CA specs would you pick?

[RNandKT]

Basedd upon the research I have done I think this profile with the conical springs would be the best. The 4 hole injectors already make it run a little rich, so I think I would still be in the range the ECU could handle.

Factory Engineered Hydraulic Cam and Tappet Package for Mild Competition Application 256-256-40* Duration, .450" Valve Lift, 108* Centerline

Thoughts guys?

[sharpxmen]

110 centerline if possible, better torque if I'm not mistaking

[RNandKT]

So I believe centerline just pushes the torque curve up or down (I don't think it actually changes the amount of torque a motor makes, just what RPM it makes it, other than of course if you get outside the valve timing). Also a larger number  I believe would push the torque curve into the higher RPMs which I think would not be what you want for a Jeep. But again I am not an expert.

[sharpxmen]

So I believe centerline just pushes the torque curve up or down (I don't think it actually changes the amount of torque a motor makes, just what RPM it makes it, other than of course if you get outside the valve timing). Also a larger number  I believe would push the torque curve into the higher RPMs which I think would not be what you want for a Jeep. But again I am not an expert.

you got it backwards, larger centerline lowers the rpm torque band, you're probably thinking of overlap